Question

Rewrite with only sin (x) and cos (x): cos (2x) - sin (x)
Can anyone help with this? Please I am so lost and it's been a while since I've worked on pre-calc

Answer 1

there are a couple ways to do this

Answer 2

they all involve using the double angle formula for cosine, but there are three ways to write it
\[\cos(2x)=\cos^2(x)-\sin(2(x)\]
\[\cos(2x)=2\cos^2(x)-1\]
\[\cos(2x)=1-2\sin^2(x)\] any one of those will work